## Efficient flattop ultra-wideband wavelength converters based on double-pass cascaded sum and difference frequency generation using engineered chirped gratings |

Optics Express, Vol. 19, Issue 23, pp. 22528-22534 (2011)

http://dx.doi.org/10.1364/OE.19.022528

Acrobat PDF (792 KB)

### Abstract

High-efficiency ultra-broadband wavelength converters based on double-pass quasi-phase-matched cascaded sum and difference frequency generation including engineered chirped gratings in lossy lithium niobate waveguides are numerically investigated and compared to the single-pass counterparts, assuming a large twin-pump wavelength difference of 75 nm. Instead of uniform gratings, few-section chirped gratings with the same length, but with a small constant period change among sections with uniform gratings, are proposed to flatten the response and increase the mean efficiency by finding the common critical period shift and minimum number of sections for both single-pass and double-pass schemes whilst for the latter the efficiency is remarkably higher in a low-loss waveguide. It is also verified that for the same waveguide length and power, the efficiency enhancement expected due to the use of the double-pass scheme instead of the single-pass one, is finally lost if the waveguide loss increases above a certain value. For the double-pass scheme, the criteria for the design of the low-loss waveguide length, and the assignment of power in the pumps to achieve the desired efficiency, bandwidth and ripple are presented for the optimum 3-section chirped-gratings-based devices. Efficient conversions with flattop bandwidths > 84 nm for lengths < 3 cm can be obtained.

© 2011 OSA

## 1. Introduction

2. K. J. Lee, S. Liu, F. Parmigiani, M. Ibsen, P. Petropoulos, K. Gallo, and D. J. Richardson, “OTDM to WDM format conversion based on quadratic cascading in a periodically poled lithium niobate waveguide,” Opt. Express **18**(10), 10282–10288 (2010), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-10-10282. [CrossRef] [PubMed]

3. Y. Wang, B. Chen, and C.-Q. Xu, “Polarisation-insensitive QPM wavelength converter with out-of-band pump,” Electron. Lett. **40**(3), 189–191 (2004). [CrossRef]

13. G.-W. Lu, S. Shinada, H. Furukawa, N. Wada, T. Miyazaki, and H. Ito, “160-Gb/s all-optical phase-transparent wavelength conversion through cascaded SFG-DFG in a broadband linear-chirped PPLN waveguide,” Opt. Express **18**(6), 6064–6070 (2010), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-6-6064. [CrossRef] [PubMed]

3. Y. Wang, B. Chen, and C.-Q. Xu, “Polarisation-insensitive QPM wavelength converter with out-of-band pump,” Electron. Lett. **40**(3), 189–191 (2004). [CrossRef]

4. K. Gallo, G. Assanto, and G. I. Stegeman, “Efficient wavelength shifting over the erbium amplifier bandwidth via cascaded second-order processes in lithium niobate waveguides,” Appl. Phys. Lett. **71**(8), 1020–1022 (1997). [CrossRef]

14. A. Tehranchi and R. Kashyap, “Improved cascaded sum and difference frequency generation-based wavelength converters in low-loss quasi-phase-matched lithium niobate waveguides,” Appl. Opt. **48**(31), G143–G147 (2009). [CrossRef] [PubMed]

15. M. Ahlawat, A. Tehranchi, C.-Q. Xu, and R. Kashyap, “Ultrabroadband flattop wavelength conversion based on cascaded sum frequency generation and difference frequency generation using pump detuning in quasi-phase-matched lithium niobate waveguides,” Appl. Opt. **50**(25), E108–E111 (2011). [CrossRef]

16. A. Tehranchi and R. Kashyap, “Engineered gratings for flat broadening of second-harmonic phase-matching bandwidth in MgO-doped lithium niobate waveguides,” Opt. Express **16**(23), 18970–18975 (2008), http://www.opticsinfobase.org/abstract.cfm?uri=oe-16-23-18970. [CrossRef] [PubMed]

12. H. Furukawa, A. Nirmalathas, N. Wada, S. Shinada, H. Tsuboya, and T. Miyazaki, “Tunable all-optical wavelength conversion of 160-Gb/s RZ optical signals by cascaded SFG-DFG generation in PPLN waveguide,” IEEE Photon. Technol. Lett. **19**(6), 384–386 (2007). [CrossRef]

13. G.-W. Lu, S. Shinada, H. Furukawa, N. Wada, T. Miyazaki, and H. Ito, “160-Gb/s all-optical phase-transparent wavelength conversion through cascaded SFG-DFG in a broadband linear-chirped PPLN waveguide,” Opt. Express **18**(6), 6064–6070 (2010), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-6-6064. [CrossRef] [PubMed]

## 2. Theory and model

*λ*

_{p}_{1}and

*λ*

_{p}_{2}, and the signal wavelength

*λ*, the wavelengths of the SF

_{s}*L*and that of

*L*to 0,

*x*axis). Also,

*L*) has been divided into

*p*sections. Each section consists of

*n*constant periods,

*p*uniform sections. The calculations begin and cascade from the first section with the length

## 3. Results and discussion

*λ*. The peak-to-peak ripple in efficiency reduces to less than 0.2 dB from 1.7 dB with a 0.3 dB decrease in the mean efficiency. On the other hand, as seen in Fig. 2(b), almost the maximum efficiency occurs without a critical period shift (δΛ = 0) for 3-section chirped gratings using the double-pass scheme in which SFG and DFG processes are independent. The peak-to-peak variation in the efficiency also reduces to less than 0.1 dB from 2.5 dB with a 0.4 dB increase in the mean efficiency. Based on the application, by choosing the optimum chirped gratings for both single- and double-pass schemes with a common number of sections, we can take advantage of the wider bandwidth using a single-pass scheme or the higher efficiency using a double-pass scheme, while we can flatten the response and increase remarkably the mean efficiency compared to those schemes using uniform gratings. Fortunately, the 3-section chirped gratings need no period shift and therefore the same grating structure on a substrate can be used for both single- and double-pass schemes (e.g., using two waveguides only one of which has a dichroic dielectric mirror at

_{SF}*p*= 1), using the double-pass scheme instead of the single-pass one, the mean conversion efficiency is increased by 3 dB but the undesired ripple is also increased by 0.8 dB and the bandwidth is decreased by 8 nm. However, for the engineered chirped gratings (

*p*= 3), even a higher mean efficiency (3.7 dB) can be achieved using the double-pass scheme as an alternative to the single-pass one, and the ripple almost vanishes for a bandwidth penalty of 10 nm.

*enhancement*for the double-pass scheme compared to the single-pass one, drops from almost 5.5 dB to 4 dB showing a 1.5 dB decrease, when the SF loss increases from 0 to 0.7 dB/cm. It is obvious that in this case, using a double-pass scheme to enhance the efficiency is only successful when the SF loss is much smaller than 2.6 dB/cm. The reason for this behaviour is that the efficiency for the double-pass scheme is decreased by a factor of

## 4. Conclusion

## Acknowledgments

## References and links

1. | T. Suhara, M. Fujimura, and M. Uemukai, “Waveguide nonlinear-optic wavelength conversion devices and their applications,” in |

2. | K. J. Lee, S. Liu, F. Parmigiani, M. Ibsen, P. Petropoulos, K. Gallo, and D. J. Richardson, “OTDM to WDM format conversion based on quadratic cascading in a periodically poled lithium niobate waveguide,” Opt. Express |

3. | Y. Wang, B. Chen, and C.-Q. Xu, “Polarisation-insensitive QPM wavelength converter with out-of-band pump,” Electron. Lett. |

4. | K. Gallo, G. Assanto, and G. I. Stegeman, “Efficient wavelength shifting over the erbium amplifier bandwidth via cascaded second-order processes in lithium niobate waveguides,” Appl. Phys. Lett. |

5. | Y. L. Lee, B. A. Yu, C. Jung, Y. C. Noh, J. Lee, and D. K. Ko, “All-optical wavelength conversion and tuning by the cascaded sum- and difference frequency generation (cSFG/DFG) in a temperature gradient controlled Ti:PPLN channel waveguide,” Opt. Express |

6. | S. Yu and W. Gu, “A tunable wavelength conversion and wavelength add/drop scheme based on cascaded second-order nonlinearity with double-pass configuration,” IEEE J. Quantum Electron. |

7. | J. Wang, J. Q. Sun, C. Lou, and Q. Z. Sun, “Experimental demonstration of wavelength conversion between ps-pulses based on cascaded sum- and difference frequency generation (SFG+DFG) in LiNbO |

8. | S. Gao, C. Yang, X. Xiao, Y. Tian, Z. You, and G. Jin, “Performance evaluation of tunable channel-selective wavelength shift by cascaded sum- and difference-frequency generation in periodically poled lithium niobate waveguides,” J. Lightwave Technol. |

9. | J. E. McGeehan, M. Giltrelli, and A. E. Willner, “All-optical digital 3-input AND gate using sum- and difference-frequency generation in PPLN waveguide,” Electron. Lett. |

10. | J. Wang, J. Sun, X. Zhang, D. Huang, and M. M. Fejer, “All-optical format conversions using periodically poled lithium niobate waveguides,” IEEE J. Quantum Electron. |

11. | A. Bogoni, X. Wu, I. Fazal, and A. E. Willner, “Photonic processing of 320 Gbits/s based on sum-/difference-frequency generation and pump depletion in a single PPLN waveguide,” Opt. Lett. |

12. | H. Furukawa, A. Nirmalathas, N. Wada, S. Shinada, H. Tsuboya, and T. Miyazaki, “Tunable all-optical wavelength conversion of 160-Gb/s RZ optical signals by cascaded SFG-DFG generation in PPLN waveguide,” IEEE Photon. Technol. Lett. |

13. | G.-W. Lu, S. Shinada, H. Furukawa, N. Wada, T. Miyazaki, and H. Ito, “160-Gb/s all-optical phase-transparent wavelength conversion through cascaded SFG-DFG in a broadband linear-chirped PPLN waveguide,” Opt. Express |

14. | A. Tehranchi and R. Kashyap, “Improved cascaded sum and difference frequency generation-based wavelength converters in low-loss quasi-phase-matched lithium niobate waveguides,” Appl. Opt. |

15. | M. Ahlawat, A. Tehranchi, C.-Q. Xu, and R. Kashyap, “Ultrabroadband flattop wavelength conversion based on cascaded sum frequency generation and difference frequency generation using pump detuning in quasi-phase-matched lithium niobate waveguides,” Appl. Opt. |

16. | A. Tehranchi and R. Kashyap, “Engineered gratings for flat broadening of second-harmonic phase-matching bandwidth in MgO-doped lithium niobate waveguides,” Opt. Express |

17. | A. Tehranchi and R. Kashyap, “Wideband wavelength conversion using double-pass cascaded χ |

**OCIS Codes**

(190.0190) Nonlinear optics : Nonlinear optics

(190.2620) Nonlinear optics : Harmonic generation and mixing

(190.4360) Nonlinear optics : Nonlinear optics, devices

**ToC Category:**

Frequency Conversion, Combs and Nonlinear Waveguides

**History**

Original Manuscript: August 30, 2011

Revised Manuscript: October 2, 2011

Manuscript Accepted: October 2, 2011

Published: October 25, 2011

**Virtual Issues**

Nonlinear Optics (2011) *Optical Materials Express*

**Citation**

Amirhossein Tehranchi, Roberto Morandotti, and Raman Kashyap, "Efficient flattop ultra-wideband wavelength converters based on double-pass cascaded sum and difference frequency generation using engineered chirped gratings," Opt. Express **19**, 22528-22534 (2011)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-23-22528

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### References

- T. Suhara, M. Fujimura, and M. Uemukai, “Waveguide nonlinear-optic wavelength conversion devices and their applications,” in Photonics Based on Wavelength Integration and Manipulation, Vol. 2 of IPAP Books (Institute of Pure and Applied Physics, 2005), pp. 137–150.
- K. J. Lee, S. Liu, F. Parmigiani, M. Ibsen, P. Petropoulos, K. Gallo, and D. J. Richardson, “OTDM to WDM format conversion based on quadratic cascading in a periodically poled lithium niobate waveguide,” Opt. Express 18(10), 10282–10288 (2010), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-10-10282 . [CrossRef] [PubMed]
- Y. Wang, B. Chen, and C.-Q. Xu, “Polarisation-insensitive QPM wavelength converter with out-of-band pump,” Electron. Lett. 40(3), 189–191 (2004). [CrossRef]
- K. Gallo, G. Assanto, and G. I. Stegeman, “Efficient wavelength shifting over the erbium amplifier bandwidth via cascaded second-order processes in lithium niobate waveguides,” Appl. Phys. Lett. 71(8), 1020–1022 (1997). [CrossRef]
- Y. L. Lee, B. A. Yu, C. Jung, Y. C. Noh, J. Lee, and D. K. Ko, “All-optical wavelength conversion and tuning by the cascaded sum- and difference frequency generation (cSFG/DFG) in a temperature gradient controlled Ti:PPLN channel waveguide,” Opt. Express 13(8), 2988–2993 (2005), http://www.opticsinfobase.org/abstract.cfm?uri=oe-13-8-2988 . [CrossRef] [PubMed]
- S. Yu and W. Gu, “A tunable wavelength conversion and wavelength add/drop scheme based on cascaded second-order nonlinearity with double-pass configuration,” IEEE J. Quantum Electron. 41(7), 1007–1012 (2005). [CrossRef]
- J. Wang, J. Q. Sun, C. Lou, and Q. Z. Sun, “Experimental demonstration of wavelength conversion between ps-pulses based on cascaded sum- and difference frequency generation (SFG+DFG) in LiNbO3 waveguides,” Opt. Express 13(19), 7405–7414 (2005), http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-13-19-7405 . [CrossRef] [PubMed]
- S. Gao, C. Yang, X. Xiao, Y. Tian, Z. You, and G. Jin, “Performance evaluation of tunable channel-selective wavelength shift by cascaded sum- and difference-frequency generation in periodically poled lithium niobate waveguides,” J. Lightwave Technol. 25(3), 710–718 (2007). [CrossRef]
- J. E. McGeehan, M. Giltrelli, and A. E. Willner, “All-optical digital 3-input AND gate using sum- and difference-frequency generation in PPLN waveguide,” Electron. Lett. 43(7), 409–410 (2007). [CrossRef]
- J. Wang, J. Sun, X. Zhang, D. Huang, and M. M. Fejer, “All-optical format conversions using periodically poled lithium niobate waveguides,” IEEE J. Quantum Electron. 45(2), 195–205 (2009). [CrossRef]
- A. Bogoni, X. Wu, I. Fazal, and A. E. Willner, “Photonic processing of 320 Gbits/s based on sum-/difference-frequency generation and pump depletion in a single PPLN waveguide,” Opt. Lett. 34(12), 1825–1827 (2009). [CrossRef] [PubMed]
- H. Furukawa, A. Nirmalathas, N. Wada, S. Shinada, H. Tsuboya, and T. Miyazaki, “Tunable all-optical wavelength conversion of 160-Gb/s RZ optical signals by cascaded SFG-DFG generation in PPLN waveguide,” IEEE Photon. Technol. Lett. 19(6), 384–386 (2007). [CrossRef]
- G.-W. Lu, S. Shinada, H. Furukawa, N. Wada, T. Miyazaki, and H. Ito, “160-Gb/s all-optical phase-transparent wavelength conversion through cascaded SFG-DFG in a broadband linear-chirped PPLN waveguide,” Opt. Express 18(6), 6064–6070 (2010), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-6-6064 . [CrossRef] [PubMed]
- A. Tehranchi and R. Kashyap, “Improved cascaded sum and difference frequency generation-based wavelength converters in low-loss quasi-phase-matched lithium niobate waveguides,” Appl. Opt. 48(31), G143–G147 (2009). [CrossRef] [PubMed]
- M. Ahlawat, A. Tehranchi, C.-Q. Xu, and R. Kashyap, “Ultrabroadband flattop wavelength conversion based on cascaded sum frequency generation and difference frequency generation using pump detuning in quasi-phase-matched lithium niobate waveguides,” Appl. Opt. 50(25), E108–E111 (2011). [CrossRef]
- A. Tehranchi and R. Kashyap, “Engineered gratings for flat broadening of second-harmonic phase-matching bandwidth in MgO-doped lithium niobate waveguides,” Opt. Express 16(23), 18970–18975 (2008), http://www.opticsinfobase.org/abstract.cfm?uri=oe-16-23-18970 . [CrossRef] [PubMed]
- A. Tehranchi and R. Kashyap, “Wideband wavelength conversion using double-pass cascaded χ(2): χ(2) interaction in lossy waveguides,” Opt. Commun. 283(7), 1485–1488 (2010). [CrossRef]

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